1. Field of Use
This invention relates to an improved process for the preparation of aldehydes having a high ratio of linear aldehydes to branched-chain aldehydes from terminally unsaturated olefins by adjusting the carbon monoxide partial pressure downward during the hydroformylation of said olefins. More specifically, this invention relates to a process for preparing aldehydes having a high ratio of linear to branched chains by substantially continuously reducing the carbon monoxide partial pressure in the hydroformylation of terminally unsaturated olefins.
2. Prior Art
Processes, known as the oxo process and also as hydroformylation, involving the preparation of reaction mixtures containing substantial amounts of aldehydes by the catalytic reaction of olefinic compounds with carbon monoxide and hydrogen at elevated temperatures and pressures are known in the art. The aldehydes produced in said processes correspond to compounds obtained by addition of a carbonyl group and hydrogen to the olefinic bond. However, in such processes the ratio of straight-chain (linear) aldehydes to branched-chain aldehydes is relatively low.
U.S. Pat. No. 2,880,241 discloses that rhodiumcontaining catalysts are effective for the hydroformylation of olefins and that at low temperatures, such as 60.degree. to 120.degree. C., they permit the production of predominantly (75 to 90%) branched isomer.
U.S. Pat. No. 3,527,809 claims a process for production of oxygenated products comprising aldehydes having high ratios of normal to branched-chain isomers by hydroformylating an alpha olefinic hydrocarbon with carbon monoxide and hydrogen in the presence of a complex catalyst of rhodium with carbon monoxide and a triorgano phosphorous ligand and excess free ligand at temperatures of 50.degree. to 145.degree. C. and a partial pressure of carbon monoxide of from 25% to 75% or 90% of a total pressure of carbon monoxide and hydrogen of less than 450 psia. However, the reference clearly discloses continuous or stepwise addition of carbon monoxide and hydrogen during said hydroformylation to maintain the carbon monoxide and hydrogen pressure at a predetermined constant level.